Some of said containers, better known as cylinders, are used widely as containers for high-pressure industrial or medical gases, for example oxygen, air, industrial gases and gases for domestic use.
Since the gas contained in the cylinder, in order to be used, must reach the user at a pressure that is close to the atmospheric pressure or in any case considerably lower than the pressure inside said container, dispensing valves and pressure reduction units are typically connected to these containers according to various configurations.
A typical configuration of a gas dispensing system uses a high-pressure line in output from the cylinder, along which there are in series a flow control valve, which is proximate to the cylinder, and a pressure regulator, the output of which is connected to a low-pressure line, which conveys the gas to the user device.
According to a different configuration, there is provided a dispensing system in which a flow control valve and a pressure regulator are integrated in series in a single device, known as VIPR (“Valve Integrated Pressure Regulator”), so as to reduce the length of the high-pressure line.
In both embodiments, the pressure regulator, arranged externally to the cylinder, makes it possible to utilize easily the constant pressure reference provided by atmospheric pressure in order to obtain a pressure of the gas in output from the reduction unit that is constant although the pressure in the cylinder is variable and proportional to the quantity of gas in said cylinder. However, both solutions, by having a high-pressure line outside the cylinder, have safety problems, which are particularly challenging in applications in which the gas is stored at particularly high pressures and the cylinder, during use, is located in the immediate vicinity of the user and/or user device.
This problem can be solved by means of dispensing systems in which the pressure regulator is accommodated entirely within the cylinder, so that at the output of said cylinder only gas at the operating pressure is available. This solution, particularly when applied to gases compressed with pressures that are considerably higher than the atmospheric pressure, has the drawback that the internal regulator does not work with a constant reference pressure in all operating conditions.
Another problem of the solutions with an internal pressure reduction unit consists in the space occupation of said reduction unit, which must be insertable in the cylinder through a threaded coupling hole provided thereon.
For example, the use of a membrane-type reduction unit makes the space occupation of the device in the direction that lies transversely to the axis of the cylinder incompatible with the coupling hole provided on traditional cylinders. To use this reduction unit it is therefore necessary to provide cylinders that are dedicated to it, with an enlarged hole, as for the solution described in EP 1000291.